A 20-year-old British man was arrested for running the Immunicity proxy server, which provided access to 36 other websites that had been blocked for offering illegal or infringing content, the U.K. Police Intellectual Property Crime Unit (PIPCU) said Thursday.

The arrest is part of the City of London Police unit’s ongoing drive to clamp down on websites providing access to illegal or infringing content, PIPCU said in a news release. The unit is targeting every aspect of how copyright-protected material is illegally being made available to Internet users, it said.

The man, whose name was not revealed, was arrested in Nottingham and released on bail after he was questioned by detectives and after he voluntarily handed over the domain names of the sites, the police said, adding that those Web pages now show a police warning banner.

“We will come down hard on people believed to be committing or deliberately facilitating such offences,” detective chief inspector and head of PIPCU, Andy Fyfe, said in a statement.

Earlier this week PIPCU banners appeared on Immunicity as well as other proxy sites, as first reported by TorrentFreak. The other sites include Piratereverse.info, a Pirate Bay proxy, and Kickassunblock.info and Katunblock.com, both KickassTorrents proxies.

Immunicity allowed users to configure their browsers to route requests via a proxy server to access blocked websites. The proxy enabled a direct connection to a point on the Internet where the sites that are blocked in the U.K. are accessible. Sites that were unblocked by the service included the Pirate Bay, Kickass Torrents, h33t and several other torrent sites, according to a YouTube video promoting the service.

Visitors to Immunicity and the other sites see a banner warning them that they have tried to access a website that is under criminal investigation by PIPCU. “This site is being investigated for online copyright infringement,” it reads.

The police operation was supported by the Federation Against Copyright Theft (FACT), which called the operation “a major step” in tackling those who provide unblocking services.

Jim Killock, executive director of the Open Rights Group (ORG), a digital civli rights group, noted that the arrested man is young and appears not to have been running the proxy service for profit. These matters have to be noted to determine whether the man’s actions were criminal, Killock said. “One could wonder whether the police had to be involved at this point,” he said.

“I suspect he has done this because he feels annoyed at the Internet being censored, and this is kind of a personal protest rather than an attempt to simply encourage infringements,” Killock said. However, the man could have had a better defense if his service did not merely provide access to censored torrent sites, but was used as a more general unblocking tool, he added. Proxy services are often used to allow people in repressive regimes to access legitimate sites that are censored in their home countries.